This invention relates to tufting machines, and more particularly to yarn feed roller pattern attachments having a plurality of feed rollers permitting each yarn end to be controlled individually thereby permitting a full repeat design across the full width of the tufting machine.
Wide use is made of yarn feed roller pattern attachments or assemblies for producing variations in pile height in tufted pile fabrics such as carpeting. Although other types of pattern attachments are used, such as those having slotted slats, the feed roller attachments are the most popular. Representative of such feed roller pattern assemblies are those disclosed in the following U.S. Pat. Nos. 2,862,465 to Card; 2,875,714 to Nix; 2,966,866 to Card; 3,001,388 to MacCaffray; 3,075,482 to Card; 3,103,187 to Hammel; 3,134,529 to Beasley; 3,272,163 to Erwin, et al; 3,375,797 to Gaines; 3,489,326 to Singleton; 3,605,660 to Short; 3,752,094 to Short; 3,847,098 to Hammel; 3,926,132 to Lear, et al; 3,955,514 to Prichard et al; 4,134,348 to Scott and 4,608,935 to Bardsley.
These assemblies include a plurality of yarn feed rollers which feed yarn to the needles of the tufting machine. Each of the feed rollers is selectively driven at one of a plurality of different speeds independently of the other feed rollers by means of clutches controlled by a pattern control. The amount of yarn supplied to the needles of the tufting machine is determined by the rotational speed of the feed rollers about which the yarn is wound, so that with a fixed needle stroke the amount of yarn supplied to each needle determines the pile height of the fabric produced. To create patterned pile effects the amount of yarn fed to the individual needles may be varied by driving the feed rollers selectively at the different speeds. As is well known in the art when less yarn is fed than required by the needle, yarn is pulled back or back-robbed from the previous stitch which then becomes a lower loop. Thus, high and low loops may be produced, or even three levels of loop when feed rollers of three different speeds are provided, and also cut and loop pile may be produced as described in Card U.S. Pat. No. 3,084,645.
Each needle receiving yarn from a given feed roller always produces a pile loop at the same height as that of the other needles receiving yarn from that roller and, therefore, the number of pattern repeats across the width of the work product is determined and limited by the number of needles receiving yarn from each roller. It is therefore clear that a limitation on the number of feed rollers restricts the carpet or rug designer to designs which repeat frequently across the width of the carpet or rug. Accordingly, it is desirable to have a pattern attachment with an increased number of feed rollers so that the number of repeats across the width of the product may be reduced, and ideally of such a number that substantially individual yarn end control may be possible. In that case a full repeat design, i.e., a design with no repeats across the full width of the machine, may be possible.
An additional reason for desiring an individual yarn end pattern attachment is that the utilization of feed roller attachments in the prior art necessitates the use of a tube bank such as that disclosed in Card U.S. Pat. No. 2,862,465 for directing the yarn fed from a particular feed roller to all the needles receiving yarn from that feed roller. Such a tube bank, of necessity, has long tubes and short tubes to direct the yarn to the various needles across the width of the machine. Because of this and because of the elasticity of the yarn the amount of yarn pull-back varies to the different needles. That is, there is a variation in the amount of pull-back for the yarns traveling the long path in the long tubes compared to the amount of pull-back for the yarns traveling the short path in the shorter tubes. Thus, for example, the pull-back in a short tube may require only one stitch when changing from high loop to a lower loop, while the pull-back in a long tube may require three stitches to make this change. Consequently, due to the variations resulting, certain patterns such as those having straight lines, e.g. checker boards, etc., cannot be produced aesthetically. A tube bank, however, would not be required with a pattern attachment having individual yarn end control.
The most successful prior art feed roller attachments have been those such as illustrated in the aforesaid Singlton, Hammel U.S. Pat. No. 3,847,098, Lear et al and Bardsley patents, in the first three of which rollers are journalled on driven shafts and electromagnetic clutch elements are mounted within the rollers for drivingly transmitting the rotation of the shaft to the rollers selectively, and in the latter patent electromagnetic clutch elements are mounted on drive shafts driven at different speeds and selectively actuated to gear the rollers to a selective shaft. Whether the electromagnetic clutches are within the rollers or are coupled to the rollers by gears, the rollers are relatively wide and therefore limits the number of rollers that can be utilized due to space limitations. Moreover, since these feed roller attachments comprise a large number of clutches, and since certain of the clutch elements have a relatively short life, frequent servicing of the roller units has been occasioned.
As aforesaid, due to space limitations prior art designs have not generally been adoptable to the large number of rollers required for individual yarn end control. The Scott, Gaines, Short, and Prichard et al patents were attempts toward this end. However, the Short and Prichard et al proposals necessitated complicated drive constructions while the Scott proposal was found impracticable and was not developed. The Gaines proposal is the closest prior art development to attaining single end control. This proposal, however, has only been used for sample machines which have relatively narrow widths because of the large number of moving parts resulting in a complicated and expensive attachment for a full width machine.